[derff96963]

I have a 2000 XJ with 4.0 I6 with a KNN FIPK. Other than that the engine is completely stock. What I don't like is just recently it doesn't idle very well. Its does idle and has never stalled on me but I just don't like how it idles. The other day I was stuck in traffic in some road construction and after about 5 minutes of not moving it started shaking pretty bad. Again it did not stall and it revs fine and has lots of power. I have checked and cleaned the throttle body and the check engine light is not on. I have changed the spark plugs with no change. I cleaned the IAC valve and it does seem to operate nomaly and the TPS tests ok to. It only has 61,000 miles on it. Anyone have this problem or have any ideas?

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).